It is becoming increasingly common to use Micro-Electro-Mechanical Systems, abbreviated as “MEMS” in a variety of applications. MEMS are micro-sized mechanical devices that are built onto semiconductor chips. In the research labs since the 1980s, MEMS devices began to materialize as commercial products in the mid-1990s. They are used to make pressure, temperature, chemical and vibration sensors, light reflectors and switches as well as accelerometers for airbags, vehicle control, pacemakers and games. The technology is also used to make ink jet print heads, micro-actuators for read/write heads and all-optical switches that reflect light beams to the appropriate output port.
MEMS are often used in conjunction with devices that utilize a piezoelectric component coupled to a pair of electrodes to actuate a switch. In general, during the fabrication of a piezoelectric MEMS switch, the switch undergoes heating to high temperatures (in excess of about 550 Centigrade, and often 660-700 Centigrade) as the piezoelectric component is annealed, or deposited if high temperature deposition is used. These high temperatures significantly degrade the morphology of metallic switch components such as switch contacts and adversely affect their electrical properties.
Attempts have been made to avoid subjecting the metallic components of the MEMS switch to high temperatures. For example, U.S. patent publication number 2004-94815 shows a bulky switch produced by preparing each of the two contacts of the switch on a separate wafer after any high temperature processes. The wafers are then stacked so that the contacts register and form the switch. The method results in a bulky switch that is costly to manufacture.
In a more typical design, such as that shown in U.S. patent publication number 2005-0151444, the MEMS switch is fabricated on a single wafer and metallic contacts are subjected to high temperatures during a piezoelectric annealing step. The publication shows a MEMS switch using multilayer piezoelectric (PZT) film. It uses PECVD SiO2 as a sacrificial layer that is removed by wet etching.
Accordingly, it is desirable to develop a method of making a MEMS switch that does not subject metal components of the switch to annealing temperatures. In addition, it is desirable to maintain the compact size of the switch and to avoid the use of multiple wafers to build each contact of the switch separately. Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.